Variable angle reverse humeral tray

ABSTRACT

A partial reverse shoulder prosthesis includes a humeral stem and a variable angle tray including a plate including a through hole including at least two cutouts oriented horizontally across from one another, and a repositionable variable angle stem occupying at least a portion of an internal cavity defined by the through hole and including a first washer including threads at least partially defining a first opening, a post at least partially occupying the internal cavity, and a pin insertable into the first opening and having a threaded head sized to engage the threads of at least one of the first washer and the post; wherein the wall of the internal cavity is sized to retain the first washer and at least a portion of the post.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/464,429 filed May 4, 2012, issued as U.S. Pat. No. 8,814,941 on Aug.26, 2014, and entitled “Variable Angle Reverse Humeral Tray,” thedisclosure of which is expressly incorporated in its entirety herein bythis reference.

TECHNICAL FIELD

The present disclosure relates to retention devices for surgicalprocedures and, more specifically, relates to variable angle prostheticcomponents including reverse shoulder prostheses.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present disclosure, a partialreverse shoulder prosthesis is provided and comprises a humeral stem anda variable angle tray adapted to be coupled to the humeral stem. Thevariable angle tray comprises a plate including a through hole at leastpartially defined by a wall that at least partially defines an internalcavity, the through hole including at least two cutouts orientedhorizontally across from one another, and a variable angle stemoccupying at least a portion of the internal cavity, the variable anglestem being selectively axially repostionable with respect to the plateto change the axial position of the variable angle stem with respect tothe plate. The variable angle stem comprises a first washer includingthreads at least partially defining a first opening and being insertableinto the internal cavity, a post at least partially occupying theinternal cavity, the post including a tapered crown and an appendageaxially extending from the plate, where the appendage is sized to bereceived by the humeral stem via a friction fit, and a pin including athreaded head and a longitudinal shaft extending from the threaded head,the pin being insertable into the first opening, where the threaded headis sized to engage the threads of at least one of the first washer andthe post. In accordance to this specific embodiment, the wall is sizedto retain the first washer and at least a portion of the post within thethrough hole.

In accordance with another embodiment of the present disclosure, apartial reverse shoulder prosthesis comprises a humeral stem and avariable angle tray adapted to be coupled to the humeral stem. Thevariable angle tray comprises a plate including a through hole at leastpartially defined by a wall that at least partially defines an internalcavity, the through hole including at least two cutouts orientedhorizontally across from one another, and a variable angle stemoccupying at least a portion of the internal cavity, the variable anglestem being selectively axially repostionable with respect to the plateto change an axial position of the variable angle stem with respect tothe plate, the variable angle stem comprising a first washer includingthreads at least partially defining a first opening and being insertableinto the internal cavity, a second washer defining a second opening andbeing insertable into the through hole, the second washer including awidthwise dimension substantially greater than a thickness of the secondwasher, a post at least partially occupying the internal cavity, thepost including threads, a tapered crown and an appendage axiallyextending from the plate, where the appendage is sized to be received bythe humeral stem via a friction fit, and a pin including a threaded headand a longitudinal shaft extending from the threaded head, the pin beinginsertable into the first opening, where the threaded head is sized toengage the threads of at least one of the first washer and the post. Inaccordance with this embodiment, the wall is sized to retain the firstwasher and at least a portion of the post within the through hole.

In accordance with yet another embodiment of the present disclosure, apartial reverse shoulder prosthesis comprises a humeral stem and avariable angle tray adapted to be coupled to the humeral stem, thevariable angle tray comprising a plate including a through hole at leastpartially defined by a wall that at least partially defines an internalcavity, the through hole including at least two cutouts orientedhorizontally across from one another, and a variable angle stemoccupying at least a portion of the internal cavity, the variable anglestem being selectively axially repostionable with respect to the plateto change an axial position of the variable angle stem with respect tothe plate. The variable angle stem comprises a first washer includingthreads at least partially defining a first opening and being insertableinto the internal cavity, a post at least partially occupying theinternal cavity, the post including threads, a tapered crown and anappendage axially extending from the plate, where the appendage is sizedto be received by the humeral stem via a friction fit, and a pinincluding a threaded head and a longitudinal shaft extending from thethreaded head, the pin being insertable into the first opening, wherethe threaded head is sized to engage the threads of at least one of thefirst washer and the post. The wall is sized to retain the first washerand at least a portion of the post within the through hole, and the postincludes a hollow adapted to receive at least a portion of thelongitudinal shaft of the pin.

In accordance with still another embodiment of the present disclosure, apartial reverse shoulder prosthesis comprises a humeral stem, a humeralcup, and a variable angle tray adapted to be coupled to the humeral stemand the humeral cup, the variable angle tray comprising a plateincluding an arcuate wall at least partially defining an internalcavity, the through hole including at least two cutouts orientedhorizontally across from one another, a bearing adapted to occupy atleast a portion of the internal cavity, the bearing being axially androtationally repositionable with respect to the plate, the bearingoperative to selectively expand in at least one dimension to wedge thebearing against the arcuate wall to inhibit axial and rotationalrepositioning of the bearing with respect to the plate, and a projectionadapted to be coupled to the humeral stem in order to mount the variableangle tray to the humeral stem. The arcuate wall is sized to retain aportion of the bearing within the internal cavity, and the bearingcomprises a plurality of washers and a threaded fastener.

Still other objects and benefits of the invention will become apparentfrom the following written description along with the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned aspects of the present invention and the manner ofobtaining them will become more apparent and the invention itself willbe better understood by reference to the following description of theembodiments of the invention taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a frontal representation of bones, overlaid by skin, of ahuman shoulder region subsequent to a shoulder replacement where areverse shoulder prosthesis has been implanted;

FIG. 2 is a cross-sectional view of a first exemplary partial shoulderjoint implant;

FIG. 3 is a top view of the exemplary plate shown in FIG. 2;

FIG. 4 is a cross-sectional view taken along lines 3-3 of FIG. 3;

FIG. 5 is a profile view of the exemplary washer of FIG. 2;

FIG. 6 is an elevated perspective view of the exemplary washer of FIG.5;

FIG. 7 is an elevated perspective view of the exemplary pin of FIG. 2;

FIG. 8 is an elevated perspective view of the exemplary post of FIG. 2;

FIG. 9 is an elevated perspective view of the exemplary spring washer ofFIG. 2;

FIG. 10 is a profile view of an exemplary tool for use with theexemplary partial shoulder joint implant of FIG. 2;

FIG. 11 is an elevated perspective view of a distal end of the exemplarytool of FIG. 10;

FIG. 12 is a cross-sectional view of an alternate exemplary plate takenalong line 13-13 of FIG. 13; and

FIG. 13 is a top view of the alternate exemplary plate of FIG. 12.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the exemplification set outherein illustrates embodiments of the invention, in several forms, theembodiments disclosed below are not intended to be exhaustive or to beconstrued as limiting the scope of the invention to the precise formsdisclosed.

DETAILED DESCRIPTION

The embodiments of the present invention described below are notintended to be exhaustive or to limit the invention to the precise formsdisclosed in the following detailed description. Rather, the embodimentsare chosen and described so that others skilled in the art mayappreciate and understand the principles and practices of the presentinvention.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any method andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the specific methodsand materials are now described. Moreover, the techniques employed orcontemplated herein are standard methodologies well known to one ofordinary skill in the art and the materials, methods and examples areillustrative only and not intended to be limiting.

The exemplary embodiments of the present disclosure are described andillustrated below to encompass retention devices for surgical proceduresand methods of fabricating the retention devices and using the retentiondevices in a surgical procedure. Of course, it will be apparent to thoseof ordinary skill in the art that the preferred embodiments discussedbelow are exemplary in nature and may be reconfigured without departingfrom the scope and spirit of the present invention. However, for clarityand precision, the exemplary embodiments as discussed below may includeoptional steps, methods, and features that one of ordinary skill shouldrecognize as not being a requisite to fall within the scope of thepresent invention.

Referencing FIGS. 1 and 2, a first exemplary partial shoulder jointimplant 100 comprises a portion of a reversible ball and socket joint.The ball portion of the joint is adapted to be coupled to a scapula 102,and includes a scapula retainer 104 and a scapula ball 108. In contrast,the socket portion of the joint comprises a humeral shaft 110 seatedwithin an intramedullary canal of a proximal humerus 112 having ahumeral cup 114 mounted to a variable angle tray 116 that is coupled tothe humeral shaft.

As shown in FIGS. 3 and 4, the variable angle tray 116 includes a plate120 having an oblong vertical profile. Generally centered within theplate 120 is a through orifice 122 extending between top and bottomsurfaces 124, 126. The vertical cross-section of the through orifice 122is not constant, but rather changes along an axis extending verticallythrough the orifice. More specifically, an inner circumferential wall130 of the plate 120 partially defines a spherical cavity 132 where thediameter of the through orifice 122 is at a minimum at the top andbottom surfaces 124, 126, but is at a maximum at the vertical midpointof the through orifice. In this first exemplary plate 120, the sphericalcavity is partially defined by a removable cap 136 that includes threads138 that engage corresponding threads 140 of a primary portion 142 ofthe plate. In this fashion, the cap 136 may be disengaged from theprimary portion 142 in order to allow components to be seated within thespherical cavity 132 and thereafter reattached to the primary portion toinhibit certain components from egressing from the spherical cavity. Theunderside of the cap 136 includes an inner circumferential wall 144 thatpartially defines the spherical cavity 132. The diameter of the innercircumferential wall 144 increases from the underside of the cap 136 tothe top planar surface 146 of the cap having an opening 148 formedtherein to accept the pin 160.

Alternatively, the cap 136 need not threadably engage the primaryportion 142 of the plate 120. Instead, the threaded cap 136 may besecured to the primary portion 142 by using a snap ring or a taper (notshown) received within a corresponding cavity of the primary portion.

Referencing FIGS. 2-6, a washer 150 is adapted to be seated within thespherical cavity 132. This washer 150 comprises a Belleville washerhaving a convex, rounded exterior surface 152 (that may be smooth ortextured) that converges and meets a substantially planar exteriorsurface 154. The rounded exterior surface 152 may include one or moredepressions 155 that circumscribe an orifice 156 extending linearlythrough the rounded exterior surface 152 at its apex. As will bediscussed in more detail hereafter, the one or more of the depressions155 are adapted to receive projections from a driver 260 that may beused to retain the relative orientation of the washer. The throughorifice 156 is substantially perpendicular to the planar exteriorsurface 154 and is delineated by a circumferential, circular wall havinga series of threads 158 adapted to be engaged by a pin 160.

While the washer 150 is shown in exemplary form as a continuous washer,it is also within the scope of the disclosure for the washer to includea radial cut 157 (shown in phantom) that renders the washerdiscontinuous. In this manner, the circumferential dimension of thewasher 150 can more readily expand and contract depending upon thepresence or absence of the pin 160. Moreover, while the washer is shownin exemplary form as a Belleville washer, it should also be known thatone may use a helical washer, a wave spring washer, or a helical coil inplace of the spring washer.

Referring to FIGS. 2-7, the pin 160 comprises a cylindrical shaft 162having a convex, semispherical distal end 164. Opposite the distal end164 is a proximal end 166 including a substantially planar surface 168that circumscribes an opening extending into the interior of theproximal end to create a proximal cavity 170. In exemplary form, thisproximal cavity 170 is delineated by a series of vertical walls 172having a hexagonal configuration. An outer circumference of the proximalend 164 includes a series of threads 174 sized to engage the threads ofthe 158 of the washer 150. In this manner, the pin 160 may extend intothe orifice 156 of the washer 150 and be vertically repositioned thereinby rotating the pin with respect to the washer. In addition to engagingthe washer 150, the pin 160 is also adapted to engage a post 180.

Referencing FIG. 8, the post 180 comprises an elongated stem 182 with agenerally circular axial cross-section that tapers from proximal todistal. A proximal end 184 of the post 180 includes a generally planartop surface with a circular edge 186 defining the circumferentialboundary of the adapter. Inset and centered with respect to the circularedge 186 is a depression 190 formed into the interior of the post 180.In exemplary form, the depression is bounded by a semispherical wall 192having a diameter that is large enough to accommodate a portion of theproximal end 164 of the pin 160. More specifically, in this exemplaryembodiment, the diameter of the semispherical wall 192 is one and a halftimes the diameter of the pin 160.

Extending proximally from the circular edge 186, a peripheral surface196 of the post 180 embodies the curvature of a partial sphere andtapers from proximal to distal until reaching a conical surface 198 thatcircumscribes a frustoconical projection 200 having a substantiallyplanar distal surface 202. In exemplary form, the horizontalcross-section of the frustoconical projection 200 is circular, thediameter of which decreases from proximal to distal between the endpointof the peripheral surface 196 and the circular perimeter of the planardistal surface 202. In this manner, the frustoconical projection 200 iscentered along a longitudinal axis 204 that vertically extends throughthe depression 190.

Referencing FIG. 9, a spring washer 210 is adapted to interpose thefirst washer 150 and the post 180 when positioned within the sphericalcavity 132. The function of the spring washer 210 is to force therounded exterior surface 152 of the first washer 150 and the peripheralsurface 196 of the post 180 against the inner circumferential walls 130,144 of the plate 120 and cap 136. The force of the spring washer ischosen to allow axial and rotational repositioning of the assembly (post180 and washers 150, 210), but provide sufficient resistance torotational motion of the first washer 150 so that this washersubstantially stays in a fixed position when the pin 160 is insertedinto the orifice 156 and rotated so the threads 158, 174 engage oneanother and the pin vertically advances with respect to the firstwasher.

In this exemplary embodiment, a domed spring washer 210 is utilized.This spring washer 210 includes a convex top surface 214 and a concavebottom surface that are generally parallel to one another and are spacedapart by a thickness dimension. An orifice 216 is axially centered andextends through the spring washer 210. In this exemplary embodiment, theorifice is generally circular. But it should be noted that other shapedorifices could be alternatively used. The outer periphery 218 of thespring washer 210 takes on a circular shape so that the washer has aconstant radial distance between the outer periphery and the boundarydefining the orifice 216 along the entire circumference, to provide aring shape. In this exemplary embodiment, the spring washer 210 isfabricated from a metal that includes material properties providingpartial elasticity that allows the washer to be compressed (from top andbottom) and spring back into shape when not compressed.

Referring to FIGS. 10 and 11, an exemplary tool 240 for use with thepartial shoulder joint implant 100 includes an outer housing 242defining a cylindrical bore occupied by an inner shaft 244 that islongitudinally and rotatably repositionable with respect to the outerhousing. The distal end 246 of the outer housing 242 includes fourprojections 248 evenly spaced and oriented in a circular pattern. Inthis exemplary embodiment, each projection 248 includes an outer arcuatesurface 250 spaced apart from an inner arcuate surface 252 by two planarside surfaces 254 and a bottom surface 256. As will be discussed in moredetail below, the projections 248 are adapted to be received within therecesses 155 of the washer 150 in order to inhibit rotation of thewasher with respect to the inner shaft 244. At a distal end of the innershaft 244 is a hexagonal driver 260 having six vertical sidewalls and asubstantially planar bottom surface 264. Again, as will be discussed inmore detail below, the driver 260 is adapted to be received within theproximal cavity 170 of the pin 160 in order to rotate of the pin withrespect to the outer housing 242 and the washer 150.

Referring to FIGS. 1-9, assembly of the partial shoulder joint implant100 includes seating the humeral shaft 110 within the intramedullarycanal of the proximal humerus 112. To ensure the shaft 110 maintains itsposition with respect to the humerus 112, the shaft 110 may incorporatebone ingrowth materials or features in addition to the use of adhesivesor cements interposing the shaft and humerus. This shaft 110 may includea socket adapted to directly receive a portion of the elongated stem 182of the post 180 via a friction fit, thereby inhibiting relative movementbetween the post 180 and shaft 110. Conversely, the shaft 110 mayinclude a socket adapted to directly receive a stem adapter 230, whichitself includes a cavity 232 for receiving a portion of the elongatedstem 182 of the post 180. Relative movement between the stem adapter 230and the humeral shaft 110 is inhibited after the adapter and shaft aresecured via a friction fit. Alternatively, or in addition, the stemadapter 230 may be mounted to the humeral shaft 110 using an adhesive orcement. For purposes of explanation, the assembly will be discussed toinclude a stem adapter 230.

After the shaft 110 is mounted to the humerus 112 and the stem adapter230 is mounted to the shaft 110, the variable angle tray 116 may bemounted to the stem adapter. Prior to mounting the variable angle tray116 to the stem adapter 230, at least a portion of the tray must beassembled. Assembly of the tray 116 begins with the plate 120 withoutthe humeral cup 114 or the removable cap 136 being mounted thereto andwithout any components being seated within the spherical cavity 132.Thereafter, the post 180 is inserted into the orifice 122 so that aportion of the elongated stem extends beyond the bottom surface 126 ofthe plate 120. Generally, the peripheral surface 196 of the post 180will contact the inner circumferential wall 130. Given that the diameterof the orifice 122 is greater than the diameter of the elongated stem182, but less than the diameter of the proximal end 184 of the post 180,the post is able to be rotationally and axially repositioned withrespect to the tray 120.

After the post 180 is inserted into the tray 120, the spring washer 210is inserted into the spherical cavity 132 so that the orifice 216 isaxially aligned with the depression 190 of the post 180. Thereafter, thewasher 150 is inserted into the spherical cavity 132 so its orifice 156is axially aligned with the orifice 216 of the spring washer 210 and thedepression 190 of the post 180. At this point, after the washer 150,spring washer 210 and post 180 have been inserted into the sphericalcavity 132, the cap 136 is mounted to the plate 120 via a threadedconnection between the threads 138 of the cap and threads 140 of theplate. The cap 136 is rotated with respect to the plate 120 until thecap can no longer be rotated, thereby securing the cap to the plate viaa friction fit. At this time, the washer 150, spring washer 210 and thepost 180 cannot be removed from the spherical cavity 132. But thecompilation of the washer 150, spring washer 210 and the post 180 arerotationally and axially repositionable within the spherical cavity 132at this point.

In order to lock the position of the washer 150, spring washer 210 andthe post 180 within the spherical cavity 132, the pin 160 is inserted(distal end 164 first) through the opening 148 of the cap 136, throughthe orifice 156 of the washer, and through the orifice 216 of the springwasher 210. Eventually, the pin 160 is inserted deep enough that itsthreads 174 engage the threads 158 of the washer 150. At this point,further penetration of the pin 160 requires the pin to be rotated withrespect to the washer 150.

The tool 240 is thereafter used to rotate the pin 160 with respect tothe washer 150, as well as axially reposition the washer 150, springwasher 210 and the post 180 with respect to the plate 120. Dependingupon the desired angle a surgeon wants to set the tray 116 with respectto the humeral shaft 110, the surgeon manipulates the tool 240 to thedesired angle to lock the relative position of the washer 150, springwasher 210 and the post 180 with respect to the plate 120. In exemplaryfrom, the driver 260 is inserted into the proximal cavity 170 of the pin160 so that rotation of the driver will result in rotation of the pin inthe same direction. Likewise, the projections 248 of the outer housing242 are received within recesses 155 of the washer 150 so that if theouter housing 242 is stationary, so too is the washer. After the tool240 has engaged the pin 160 and the washer 150, the driver 260 isrotated so the threads 158, 174 engage one another to draw the pindeeper into the spherical cavity 132. At a predetermined point, thedistal end 164 of the pin 160 contacts the semicircular wall 192. Afterthis point, continued movement of the pin 160 operates to moves thewasher 150 vertically away from the proximal end 184 of the post 180 toeventually form a wedge locking the washer and post in position. Thiswedge is exhibited when no further rotational motion of the pin 160 withrespect to the post 180 is available. When the wedge is created, theaxial position of the post 180, and hence its elongated stem 182, islocked in position with respect to the plate 120. At this time, the tool240 may be removed and the tray 116 mounted to the stem adapter 230. Inthis manner, relative movement between the stem adapter 230 and the tray116 is inhibited after the adapter and tray are secured via a frictionfit. Alternatively, or in addition, the stem adapter 230 may be mountedto the tray 116 using an adhesive or cement. After the tray 116 ismounted to the stem adapter 230, the humeral cup 114 may be mounted tothe tray.

Referring to FIGS. 12 and 13, an alternate exemplary plate 320 may beused in place of the foregoing plate 120. In contrast to the foregoingplate 120, this alternate exemplary plate 320 does not include aremovable cap 136. As with the first exemplary plate 120, this alternateexemplary plate 320 includes an oblong vertical profile. Generallycentered within the plate 320 is a through orifice 322 extending betweentop and bottom surfaces 324, 326. The vertical cross-section of thethrough orifice 322 is not constant, but rather changes along an axisextending vertically through the orifice. More specifically, an innercircumferential wall 330 of the plate 320 partially defines a sphericalcavity 332 where the diameter of the through orifice 322 is at a minimumat the top and bottom surfaces 324, 326, but is at a maximum at thevertical midpoint of the through orifice. But the spherical cavity 332is not entirely spherical. A pair of cutouts 336 are formed verticallythrough the top surface 324 and radially into the plate 320 toaccommodate insertion of washers. The cutouts 336, in exemplary form,may be oriented on the same side of a diametric line and formedvertically to a midpoint of the plate 320. The dimension of the cutouts336 accommodate vertical insertion of the washers when the washers areturned so that the vertical dimension (i.e., thickness) of the washersis oriented horizontally so the washers can be inserted into thespherical cavity 332 and then axially repositioned so the verticaldimension is oriented vertically. In other words, the thickness of eachof the washers is less than the width of the cutouts 336. Because thecutouts 336 do not extend around the entire circumference of the cavity332, once the washers are inserted into the cavity and axiallyrepositioned, the washers may not be removed from the cavity unless thewashers are axially repositioned so that the horizontal position isvertically oriented.

Using the alternate exemplary plate 320 requires using a modified post180. In this manner, the elongated stem 182 is removable from theproximal end 184 via a threaded connection. More specifically, theelongated stem 182 includes a male threaded connection that is receivedwith a female threaded connection of the proximal end 184. As a result,only the proximal end 184 of the post 180 need to inserted in betweenthe cutouts 336. After the proximal end 184 of the post 180 is withinthe spherical cavity 332, the elongated stem 182 is coupled to theproximal end by engagement of the threaded connections. Beyond thesemodifications, all other aspects are substantially the same as the firstexemplary embodiment.

Following from the above description and invention summaries, it shouldbe apparent to those of ordinary skill in the art that, while themethods and apparatuses herein described constitute exemplaryembodiments of the present invention, the invention contained herein isnot limited to this precise embodiment and that changes may be made tosuch embodiments without departing from the scope of the invention asdefined by the claims. Additionally, it is to be understood that theinvention is defined by the claims and it is not intended that anylimitations or elements describing the exemplary embodiments set forthherein are to be incorporated into the interpretation of any claimelement unless such limitation or element is explicitly stated.Likewise, it is to be understood that it is not necessary to meet any orall of the identified advantages or objects of the invention disclosedherein in order to fall within the scope of any claims, since theinvention is defined by the claims and since inherent and/or unforeseenadvantages of the present invention may exist even though they may nothave been explicitly discussed herein.

The terminology used herein is for the purpose of describing particularillustrative embodiments only and is not intended to be limiting. Asused herein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”,“lower”, “above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations).

What is claimed is:
 1. A partial reverse shoulder prosthesis comprising:a humeral stem; and a variable angle tray adapted to be coupled to thehumeral stem, the variable angle tray comprising: a plate including athrough hole at least partially defined by a wall that at leastpartially defines an internal cavity, the through hole including atleast two cutouts oriented horizontally across from one another; and avariable angle stem occupying at least a portion of the internal cavity,the variable angle stem being selectively axially repostionable withrespect to the plate to change the axial position of the variable anglestem with respect to the plate, the variable angle stem comprising: afirst washer including threads at least partially defining a firstopening and being insertable into the internal cavity; a post at leastpartially occupying the internal cavity, the post including a taperedcrown and an appendage axially extending from the plate, where theappendage is sized to be received by the humeral stem via a frictionfit; and a pin including a threaded head and a longitudinal shaftextending from the threaded head, the pin being insertable into thefirst opening, where the threaded head is sized to engage the threads ofat least one of the first washer and the post; wherein the wall is sizedto retain the first washer and at least a portion of the post within thethrough hole.
 2. The partial reverse shoulder prosthesis of claim 1,wherein the first washer is discontinuous.
 3. The partial reverseshoulder prosthesis of claim 1, wherein the at least two cutouts areboth oriented on the same side of a horizontal diametric chord of thethrough hole.
 4. The partial reverse shoulder prosthesis of claim 1,wherein at least one of the first washer and the tapered crown includesa rounded circumferential surface adapted to contact the wall.
 5. Thepartial reverse shoulder prosthesis of claim 4, wherein the roundedcircumferential surface is at least one of smooth and textured.
 6. Thepartial reverse shoulder prosthesis of claim 1, wherein at least one ofthe first washer and the tapered crown includes a sloped circumferentialsurface adapted to contact the wall.
 7. The partial reverse shoulderprosthesis of claim 6, wherein the sloped circumferential surface is atleast one of smooth and textured.
 8. A partial reverse shoulderprosthesis comprising: a humeral stem; and a variable angle tray adaptedto be coupled to the humeral stem, the variable angle tray comprising: aplate including a through hole at least partially defined by a wall thatat least partially defines an internal cavity, the through holeincluding at least two cutouts oriented horizontally across from oneanother; and a variable angle stem occupying at least a portion of theinternal cavity, the variable angle stem being selectively axiallyrepostionable with respect to the plate to change an axial position ofthe variable angle stem with respect to the plate, the variable anglestem comprising: a first washer including threads at least partiallydefining a first opening and being insertable into the internal cavity;a second washer defining a second opening and being insertable into thethrough hole, the second washer including a widthwise dimensionsubstantially greater than a thickness of the second washer; a post atleast partially occupying the internal cavity, the post includingthreads, a tapered crown and an appendage axially extending from theplate, where the appendage is sized to be received by the humeral stemvia a friction fit; and a pin including a threaded head and alongitudinal shaft extending from the threaded head, the pin beinginsertable into the first opening, where the threaded head is sized toengage the threads of at least one of the first washer and the post;wherein the wall is sized to retain the first washer and at least aportion of the post within the through hole.
 9. The partial reverseshoulder prosthesis of claim 8, wherein the at least two cutouts areboth oriented on the same side of a horizontal diametric chord of thethrough hole.
 10. The partial reverse shoulder prosthesis of claim 8,wherein the second washer is a spring washer.
 11. The partial reverseshoulder prosthesis of claim 8, wherein the second washer comprises aBelleville washer.
 12. A partial reverse shoulder prosthesis,comprising: a humeral stem; and a variable angle tray adapted to becoupled to the humeral stem, the variable angle tray comprising: a plateincluding a through hole at least partially defined by a wall that atleast partially defines an internal cavity, the through hole includingat least two cutouts oriented horizontally across from one another; anda variable angle stem occupying at least a portion of the internalcavity, the variable angle stem being selectively axially repostionablewith respect to the plate to change an axial position of the variableangle stem with respect to the plate, the variable angle stemcomprising: a first washer including threads at least partially defininga first opening and being insertable into the internal cavity; a post atleast partially occupying the internal cavity, the post includingthreads, a tapered crown and an appendage axially extending from theplate, where the appendage is sized to be received by the humeral stemvia a friction fit; and a pin including a threaded head and alongitudinal shaft extending from the threaded head, the pin beinginsertable into the first opening, where the threaded head is sized toengage the threads of at least one of the first washer and the post;wherein the wall is sized to retain the first washer and at least aportion of the post within the through hole; and wherein the postincludes a hollow adapted to receive at least a portion of thelongitudinal shaft of the pin.
 13. The partial reverse shoulderprosthesis of claim 12, wherein the at least two cutouts are bothoriented on the same side of a horizontal diametric chord of the throughhole.
 14. The partial reverse should prosthesis of claim 12, furthercomprising a humeral cup mounted to the variable angle tray.
 15. Apartial reverse shoulder prosthesis comprising: a humeral stem; ahumeral cup; and a variable angle tray adapted to be coupled to thehumeral stem and the humeral cup, the variable angle tray comprising: aplate including an arcuate wall at least partially defining an internalcavity, the through hole including at least two cutouts orientedhorizontally across from one another; a bearing adapted to occupy atleast a portion of the internal cavity, the bearing being axially androtationally repositionable with respect to the plate, the bearingoperative to selectively expand in at least one dimension to wedge thebearing against the arcuate wall to inhibit axial and rotationalrepositioning of the bearing with respect to the plate; and a projectionadapted to be coupled to the humeral stem in order to mount the variableangle tray to the humeral stem; wherein the arcuate wall is sized toretain a portion of the bearing within the internal cavity; and whereinthe bearing comprises a plurality of washers and a threaded fastener.16. The partial reverse shoulder prosthesis of claim 15, wherein the atleast two cutouts are both oriented on the same side of a horizontaldiametric chord of the through hole.
 17. The partial reverse shoulderprosthesis of claim 15, wherein: the plate includes a through openingthat communicates with the internal cavity; and the internal cavity ispartially spherical shaped.
 18. The partial reverse shoulder prosthesisof claim 15, wherein: the plurality of washers comprise a first washerand a second washer; the threaded fastener is sized to extend throughand engage a threaded hole of the first washer; the threaded fastener issized to engage the second washer; movement of the threaded fastener ina first direction with respect to the first washer causes the bearing toexpand and wedge the bearing against the arcuate wall to inhibit axialand rotational repositioning of the bearing with respect to the plate;and movement of the threaded fastener in a second direction, generallyopposite the first direction, with respect to the first washer causesthe bearing to contract and allow axial and rotational repositioning ofthe bearing with respect to the plate.
 19. The partial reverse shoulderprosthesis of claim 15, wherein the first washer includes a convexexterior surface adapted to contact the arcuate wall of the plate.
 20. Apartial reverse shoulder prosthesis system comprising: a humeral stem; avariable angle tray adapted to be coupled to the humeral stem, thevariable angle tray comprising: a plate including a through hole atleast partially defined by a wall that at least partially defines aninternal cavity, the through hole including at least two cutoutsoriented horizontally across from one another; and a variable angle stemoccupying at least a portion of the internal cavity, the variable anglestem being selectively axially repostionable with respect to the plateto change the axial position of the variable angle stem with respect tothe plate, the variable angle stem comprising: a first washer includingthreads at least partially defining a first opening and being insertableinto the internal cavity; a post at least partially occupying theinternal cavity, the post including a tapered crown and an appendageaxially extending from the plate, where the appendage is sized to bereceived by the humeral stem via a friction fit; and a pin including athreaded head and a longitudinal shaft extending from the threaded head,the pin being insertable into the first opening, where the threaded headis sized to engage the threads of at least one of the first washer andthe post, wherein the wall is sized to retain the first washer and atleast a portion of the post within the through hole; and a driverincluding a first engagement device and a second engagement device,wherein the first engagement device is rotatably repositionable withrespect to the second engagement device, wherein the first engagementdevice engages the pin, and wherein the second engagement device engagesthe first washer.